1. Field of the Invention
The present invention relates to the field of flashing the perimeters and penetrations of flat roofing systems whereby a pliable waterproofing membrane is used to cover the roof and then folded in a specified manner in order to protect the fasteners and further waterproof the building.
2. Background
In the field of flat or low-slope roof installation, the use of pliable reinforced membranes to waterproof buildings is becoming ever more popular due to their ease of use and many advantages. However, as with any roofing system, there are difficulties and complications that arise when one considers how to waterproof the perimeter of a building (at any vertical junctures such as a wall or the flat edge of the roof) as well as any projections through and above the roof. The primary difficulty arises due to the seams and vertical junctures, which create a need to terminate the membrane in a completely watertight fashion.
This difficulty of waterproofing membrane terminations in the past has been dealt with by several methods, primarily by use of a two piece membrane flashing system coupled with pre-formed sheet metal parts. Typically, on a flat roof with a parapet wall, the membrane on the horizontal part of the roof is cut at the junction between the wall and the roof. This membrane is then fastened by the same means as the rest of the flat part of the roof. Then, a separate piece of membrane is attached to the wall by means of termination bar (typically a pre-formed piece of sheet metal) and the uppermost junction of the termination bar with the wall is sealed with a bead of watertight sealant. The loose membrane below the location of the termination bar is then folded at the wall-roof junction and adhered (typically by chemical or thermal means) to the first piece of membrane on the horizontal roof, thereby covering and sealing in the fasteners.
Curbs (rectangular projections through a roof) are typically flashed in a very similar manner, requiring more fasteners than on a flat portion of the roof in order to sufficiently waterproof the penetration. There is also a pre-formed corner that is designed to fit over the corners of these penetrations. They are made of the same base material as the membrane used on the roof and are chemically compatible with said membrane. The membrane around the curb has to be fastened in the same manner as the rest of the roofing membrane and then have another separate piece of membrane covering the vertical surfaces of the curb and also covering the fasteners around its perimeter in order to protect and waterproof them.
The difficulty with using two pieces of membrane to flash the roof lies particularly in the increased labor involved. The membrane must first be fastened to the roof itself. Mechanical fasteners are typically placed from six inches to eighteen inches apart, which can amount to a considerable number of fasteners on the perimeter and penetrations of a large building. Chemical adherence (typically a specialized type of glue or tape) can be very time consuming as well. After fastening the membrane to the substrate that is already attached to the roof, a separate piece of membrane must be cut and terminated at one end then also welded to the membrane. This multi-step process requires intensive labor and time. In addition, it can be easy to make an error in this complicated process. Any portion of the membrane that does not create a perfect seal will allow moisture underneath the membrane, potentially leaking and causing damage to the substrate and roof deck.
It is the goal of the system and accompanying devices to simplify the process of installing membrane roofing on flat roofs. To be able to use only a single piece membrane flashing for edges and curbs will not only make the roof installation process simpler and less time consuming but will also decrease the likelihood of water penetrating through to the substrate and, in turn, make a more waterproof roofing system with high versatility and ease of installation. Furthermore, the system attempts to reduce potential water penetration by use of ridges in the devices and compression of the membrane at fastening points. This system will retain a high level of wind uplift resistance and maintain strength at all fastening points.
There have been previous attempts at solving some, but not all, of the above listed problems and difficulties. U.S. Pat. No. 5,619,827 attempted to solve the problem of waterproofing a roof at the edge by use of interlocking sheet metal assemblies that serve to anchor the roof as well as waterproof it. However, this system only works for situations where the roof is entirely horizontal and there is no vertical wall. In addition, it does not appear to make the roofing installation process much simpler than the current methods. This method does make use of a non-penetrative means of anchoring the membrane to the roof, which increases waterproofing capabilities simply in the fact that no hole is made in the roofing membrane. There does appear to be a question of how well the system can anchor the membrane down sufficiently, leaving it open to pulling due to thermal shrinkage and detachment due to high winds.
The most common fastening method for membranes is the stress plate, as described in U.S. Pat. No. 4,787,188. The plate's primary purpose is to clamp the membrane to the roof deck. In its most used form, the stress plate is circular, with a centrally located fastening hole, which accepts a screw or other mechanical fastener. The plate has two sets of concentric ridges. It is placed on top of the membrane and a fastener extends through the plate and to the roof deck. The prongs inhibit motion of the membrane in relation to the plate. However, since the plate is not watertight, it has to be overlapped with a separate portion of membrane, heat or chemically welded to cover the plate and fastener and waterproof them. For the inner (non-perimeter) portion of the roof, this is the most common and efficient method of fastening membrane. However, due to the lack of a seam and the need for more fasteners at the perimeter (as well as at curbs and other penetrations), there is desired a better method of waterproofing a roof and securing it to the building structure.